Wide belt sanding machine with improved support for outboard end of cantilevered center bar

ABSTRACT

A sanding machine has a wide endless abrasive belt trained around a contact drum and a tensioning roll, both journaled in bearings mounted on a cantilevered center bar. The outboard end of the center bar is rigidly supported by a spacer block removably inserted between the underside of a foot-like bracket depending from the outboard end of the center bar and the top surface of a pad vertically adjustably mounted on the frame of the machine beneath the bracket. A clamping screw that passes freely through aligned holes in the bracket and the removable spacer block, and is threaded into the vertically adjustable pad, secures the outboard end of the center bar to the frame.

United States Patent [1 1 Bernu Dec. 11, 1973 [75] Inventor: John M. Bernu, Minneapolis, Minn.

[73] Assignee: Timesavers, Inc., Minneapolis,

3,504,458 4/1970 Rutt 51/135 BT Primary Examiner-0thell M. Simpson Assistant ExaminerNicholas P. Godici Attorney-lra Milton Jones [57} ABSTRACT A sanding machine has a wide endless abrasive belt trained around a contact drum and a tensioning roll, both journaled in bearings mounted on a cantilevered center bar. The outboard end of the center bar is rigidly supported by a spacer block removably inserted between the underside ofa foot-like bracket depending from the outboard end of the center bar and the top surface of a pad vertically adjustably mounted on the frame of the machine beneath the bracket. A clamping screw that passes freely through aligned holes in the bracket and the removable spacer block, and is threaded into the vertically adjustable pad, secures the outboard end of the center bar to the frame.

8 Claims, 3 Drawing Figures PATENTEDUEC 1 1 1975 sum 10F 2 N UTm WIDE BELT SANDING MACHINE WITH IMPROVED SUPPORT FOR OUTBOARD END OF CANTILEVERED CENTER BAR This invention relates to wide belt sanding machines wherein an endless abrasive belt is trained around a lower contact drum and an upper belt tensioning roll, both of which are journaled in bearings mounted on a horizontal arm which is customarily referred to as the center bar of the machine and which extends cantilever fashion from the upright part of the main frame of the machine at one side thereof and has its outboard end at the other side of the machine.

In a wide belt sanding machine, the work performing portion of the machine known as the sanding head comprises the center bar, a contact drum and a tension roll that are rotatably mounted on the center bar, and the endless abrasive belt that is trained around the tension roll and contact drum. workpieces fed through the machine on a horizontal conveyor belt beneath the contact drum are abraded by the sanding head as they are carried under it.

Since the center bar takes all work reaction forces, it must be solidly supported at both ends. Accordingly, the outboard end of the center bar has to be supportingly connected with the adjacent main frame portion therebeneath. But to enable the endless abrasive belt to be removed and replaced when necessary, the supporting connection between the outboard end of the center bar and the main frame must be separable.

Various expedients for providing such a separable supporting connection have been proposed. See, for example, the R. D. Rutt US. Pat. No. 3,504,458 and the F. M. Owrey et al US. Pat. No. 3,520,089.

However, all such expedients heretofore available have had the serious disadvantage of requiring expensive custom fitting to the particular machine on which they were installed. The reason for this is that the frame of a belt sanding machine is fabricated as a weldment, and therefore cannot be built to very close tolerances. As a result, there is a variation from machine to machine in the size of the gap or space between the outboard end of the cantilevered center bar and'the portion of the machine frame which is beneath it and to which it must be separably connected. Hence the separable connection which spans this gap had to be carefully tailored to each particular machine.

By contrast with these prior expedients, it is an object of this invention to provide a very simple and inexpensive standarized device for rigidly supporting the outboard end of the center bar, and which can be quickly and easily adjusted to accommodate the inevitable variations in the machine frame dimensions and can be readily removed and replaced whenever replacement of the abrasive belt is required.

With these observations and objectives in mind, the manner in which the invention achieves its purpose will be appreciated from the following description and the accompanying drawings, which exemplify the invention, it being understood that changes may be made in the specific apparatus disclosed herein without departing from the essentials of the invention set forth in the appended claims.

The accompanying drawings illustrate one complete example of an embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and

, in which:

FIG. 1 is a view of a belt sanding machine embodying the principles of this invention, mainly in end elevation but with portions shown in section to illustrate details of the separable connection between the main frame structure and the outboard end of the center bar, and with the upper housing structure merely indicated with light broken lines;

FIG. 2 is a fragmentary view, mainly in elevation but partly in section, showing the separable connection as seen from the left of FIG. 1; and

FIG. 3 is an exploded perspective view of the components of the separable connection.

Referring now more particularly to the accompanying drawings, the numeral 4 designates generally the sanding head of the illustrated wide belt sanding machine, comprising an endless abrasive belt 5 trained around an upper tensioning roll 6 and a lower contact drum 7. The abrasive belt of the sanding head is pressed against the top surface of workpieces carried through the machine on the upper stretch of a conveyor belt 8 which rides on a platen, not shown. A motor 9 drivingly connected with the contact drum drives the abrasive belt at high speed; and another motor (not shown) drives the conveyor at an appropriate speed. As is customary, the entire conveyor structure is mounted on the lower base portion 10 of the main frame of the machine, for vertical adjustment to accommodate workpieces of different thicknesses.

The main frame of the machine is a weldment and at the opposite sides of its base portion 10 it has upright side frame sections 11 and 12, the former being taller than the latter. Rigidly fixed to the top of the taller side frame section 11, and extending cantilever fashion therefrom towards the other side of the machine, is a horizontal arm 13 which, in the parlance of the art, is known as the center bar of the machine. It is this part of the machine that carries the sanding head 4. Thus bearings 14 that are mounted in brackets 15l5' fixed to and depending from'the underside of the center bar, have the shaft of the contact drum journaled therein; and a yoke 16, with bearings 17 in which the tension roll is journaled, is supported on the center bar by the ram of an air cylinder 18 that is fixed to the center bar. Since the center bar is a hollow member substantially square in cross section with horizontal top and bottom walls, the air cylinder is set into the center bar and secured to its top wall.

By means of the air cylinder, the tension roll can be raised, as needed, to tension the abrasive belt and can be lowered to permit its removal and replacement.

Since the contact drum-supported abrasive belt engages the workpiece being acted upon with considerable force, and since exact parallelism is necessary between the contact drum and the platen-supported upper stretch of the conveyor belt, it is evident that the sanding head must be solidly supported against any possible deflection. Accordingly, the outboard end of the cantilevered center bar, as well as its anchored end, must be rigidly supported and tied to the frame of the machine. But the structure supporting the outboard end of the center bar must be such that it can be gotten out of the way to permit the endless abrasive belt to be removed and replaced. It is primarily in the manner in which the outboard end'of the center bar is connected to the machine frame that the present invention distinguishes from the prior art. As in the past, the connection is separable but compared with previous structures for this purpose, it is a significant and substantial improvement.

The separable connection, identified generally by the numeral 20, is made between the top of the shorter side frame section 12 and the bottom of the adjacent bearing bracket 15. Thus, this bracket which is also a weldrnent is substantially a foot with a horizontal bottom wall 21 the underside of which is flat and overlies the upwardly facing surface of the horizontal top wall 22 of the side frame section 12. It is to be noted that the space or gap between said opposing downwardly and upwardly facing surfaces is in line with the underside of the contact drum 7. Thus, when this gap is open and unrestricted, it provides a passage through which the bottom loop of the abrasive belt may be passed during removal and replacement of the belt. It is, of course, to be understood that for the abrasive belt to be removed, the tension thereon must be released and a door in the shroud 23 (shown in light broken lines) which covers the side of the machine above the side frame section 12, must be swung open.

The separable connection comprises a removable spacer block 24, a vertically adjustable pad 25 and a clamping screw 26. The vertically adjustable pad 25 has a stepped configuration with a generally square upper portion 27 and a larger laterally projecting flange-like lower portion 28. The pad is secured to the horizontal top wall 22 of the side frame section 12 with its upper portion 27 protruding upwardly through a hole 29 in the wall 22, to have its flat top surface above the level of the top wall 22. It is secured in place by counteracting screws 30 and 31. The screws 30 pass downwardly through holes in the top wall 22 and are threaded into tapped holes 32 in the lower portion 28 of the pad, and the screws 31 are threaded into tapped holes in the lower portion of the pad and bear against the underside of the wall 22. There are four of the screws 30, one at each of the four corners of the lower portion of the pad, and two screws 31 each located between two of the screws 30. By appropriate adjustment of the screws, the top surface of the pad can be accurately brought to any elevation needed to assure that upon insertion of the removable spacer block 24 between the top of the pad and the underside of the bottom wall 21 of the boat-like bracket 15 the outboard end of the cantilevered center bar will be so located that the sanding head mounted thereon will be properly positioned with respect to the platen-supported hori zontal top stretch of the conveyor belt.

The clamping screw 26ties the outboard end? of the center bar to the side frame section 12 and to do so it passes freely through a hole 39 in the bottom wall 21 of the bracket 15 and a hole 40 in the spacer block 24, and is threaded into a hole 41 in the pad. Wings 42 that project from the head of the clamping screw make it easy to tighten and/or loosen the screw; and a bail-like handle 43 that projects from the front of the spacer block facilitates its insertion and withdrawal. Preferably the upper portion 27 of the pad and the spacer block have the same size and shape in horizontal plan, so that when in operative position, the spacer block is substantially a continuation of the pad.

From the foregoing description, it will be evident that the vertical adjustability of the pad 25 completely obviates time consuming tailormaking and fitting the spacer block to a particular machine frame, and instead permits the same sized spacer block to be used with any and all machine frames, despite the dimensional variations that are inevitable in weldments; and that it also enables restoration of alignment between the sanding head and the platen-supported conveyor if, for any reason, such as working stresses in the machine, realignment becomes necessary.

While the invention has been described as applied to a machine with but one sanding head, it is of course equally applicable to machines having a number of sanding heads in tandem, even when one of the heads usually the last in the series has a pressure shoe flanked by rollers instead of a contact drum.

Those skilled in the art will appreciate that the invention can be embodied in forms other than as herein disclosed for purposes of illustration.

The invention is defined by the following claims:

1. A belt-type sanding machine having a main frame with upright side frame sections, a horizontal work support between said side frame sections and a sanding head above the work support carried by a horizontal center bar having an inboard end securely fixed to one of said side frame sections and an outboard end overlying and spaced above the other side frame section,

said sanding head having an orbitally driven endless abrasive belt which, during operation of the machine, has its downwardly facing bottom portion pressed against a workpiece on the work support along an elongated contact zone that extends transversely across the machine, and which abrasive belt must be periodically removed and replaced, and in the act thereof passes through the space between the outboard end of the center bar and the top of the adjacent side frame section,

said machine being characterized by improved means for separably connecting the outboard end of said center bar with the side frame section therebeneath, said means comprising:

A. a removable spacer block of fixed thickness;

B. structure at the underside of the outboard end of the center bar providing a substantially horizontal wall with a downwardly facing surface that is substantially bisected by a vertical plane passing thru said elongated contact zone;

C. structure on the side frame section beneath the outboard end of the center bar providing a substantially horizontal wall with an upwardly facing surface opposing said downwardly facing surface and spaced therefrom a distance greater than the thickness of said spacer block, said upwardly facing surface being directly below said downwardly facing surface and hence also substantially bisected by said vertical plane;

D. a pad vertically adjustably connected with one of said two substantially horizontal walls and having a surface that in all positions of adjustment of the pad is at an elevation between said opposing surfaces and faces the other of said walls and is also substantially bisected by said vertical plane;

E. means for adjusting the elevation of said pad with respect to the wall with which it is connected and for securing said pad in an adjusted position at which its said surface is so spaced from the surface of the wall it faces that insertion and clamping of the spacer block between said facing surfaces accurately locates the sanding head with respect to the work support; and F. clamping means operable to draw said two substantially horizontal walls towards one another and thereby clamp said surfaces between which the spacer block is inserted tightly against the block. 2. In a belt-type sanding machine, the characterizing structure of claim 1, wherein it is the horizontal wall provided by the structure on the side frame section with which said pad is connected.

3. In a belt-type sanding machine, the improvement set forth in claim 2, further characterized in that said structure at the underside of the outboard end of the center bar comprises a bracket fixed to the center bar and depending therefrom a distance such that the downwardly facing surface provided thereby and which constitutes the bottom of said bracket is at a level close to that of the downwardly facing bottom portion of the endless abrasive belt. 4. In a belt-type sanding machine, the structure of claim 3, further characterized by a pressure applying member extending across the bottom portion of the endless abrasive belt to press the same against a workpiece on the work support. 5. In a belt-type sanding machine, the structure of claim 4, wherein said pressure applying member is a contact roll journaled in coaxial bearings fixed with respect to and located below the center bar with the axis of said bearings coinciding with said vertical plane,

and wherein one of said bearings is mounted on said bracket which provides the said downwardly facing surface. 6. In a belt-type sanding machine, the improvement of claim 2, further characterized in that:

said pad has a stepped configuration with an upper portion rising from a flange-like lower portion; wherein said horizontal wall with which the pad is connected has a hole of a size and shape to accommodate the upper portion of the pad but not its flange-like lower portion;

wherein the upper portion of the pad projects through the hole in said wall and the lower portion of the pad underlies the underside of said wall; and wherein said means for adjusting the elevation of the pad and securing it in adjusted position comprises a plurality of screws passing downwardly through holes in said horizontal wall and threaded into holes in the flange-like bottom portion of the pad and by which the pad may be drawn upwardly with respect to said horizontal wall, and other screws having threaded connection with the flange-like lower portion of said horizontal wall and bearing against the underside of said wall to draw the pad downward.

7. In a belt-type sanding machine, the structure set forth in claim 6, further characterized in that said spacer block has flat parallel top and bottom surfaces and in plan has substantially the same size and shape as the upper portion of the pad,

so that when in operative position, the spacer block is substantially an upward continuation of the upper portion of the pad,

and further characterized by handle means on the spacer block to facilitate its placement into and withdrawal from operative position.

8. In a belt-type sanding machine, the improvement set forth in claim 2 wherein said clamping means comprises a clamping screw which passes freely through aligned holes in the substantially horizontal wall provided by the structure at the underside of the outboard end of the center bar and in the spacer block, and has a head bearing on said substantially horizontal wall and a threaded connection with said pad. 

1. A belt-type sanding machine having a main frame with upright side frame sections, a horizontal work support between said side frame sections and a sanding head above the work support carried by a horizontal center bar having an inboard end securely fixed to one of said side frame sections and an outboard end overlying and spaced above the other side frame section, said sanding head having an orbitally driven endless abrasive belt which, during operation of the machine, has its downwardly facing bottom portion pressed against a workpiece on the work support along an elongated contact zone that extends transversely across the machine, and which abrasive belt must be periodically removed and replaced, and in the act thereof passes through the space between the outboard end of the center bar and the top of the adjacent side frame section, said machine being characterized by improved means for separably connecting the outboard end of said center bar with the side frame section therebeneath, said means comprising: A. a removable spacer block of fixed thickness; B. structure at the underside of the outboard end of the center bar providing a substantially horizontal wall with a downwardly facing surface that is substantially bisected by a vertical plane passing thru said elongated contact zone; C. structure on the side frame section beneath the outboard end of the center bar providing a substantially horizontal wall with an upwardly facing surface opposing said downwardly facing surface and spaced therefrom a distance greater than the thickness of said spacer block, said upwardly facing surface being directly below said downwardly facing surface and hence also substantially bisected by said vertical plane; D. a pad vertically adjustably connected with one of said two substantially horizontal walls and having a surface that in all positions of adjustment of the pad is at an elevation between said opposing surfaces and faces the other of said walls and is also substantially bisected by said vertical plane; E. means for adjusting the elevation of said pad with respect to the wall with which it is connected and for securing said pad in an adjusted position at which its said surface is so spaced from the surface of the wall it faces that insertion and clamping of the spacer block between said facing surfaces accurately locates the sanding head with respect to the work support; and F. clamping means operable to draw said two substantially horizontal walls towards one another and thereby clamp said surfaces between which the spacer block is inserted tightly against the block.
 2. In a belt-type sanding machine, the characterizing structure of claim 1, wherein it is the horizontal wall provided by the structure on the side frame section with which said pad is connected.
 3. In a belt-type sanding machine, the improvement set forth in claim 2, further characterized in that said structure at the underside of the outboard end of the center bar comprises a bracket fixed to the center bar and depending therefrom a distance such that the downwardly facing surface provided thereby and which constitutes the bottom of said bracket is at a level close to that of the downwardly facing bottom portion of the endless abrasive belt.
 4. In a belt-type sanding machine, the structure of claim 3, further characterized by a pressure applying member extending across the bottom portion of the endless abrasive belt to press the same against a workpiece on the work support.
 5. In a belt-type sanding machine, the structure of claim 4, wherein said pressure applying member is a contact roll journaled in coaxial bearings fixed with respect to and located below the center bar with the axis of said bearings coinciding with said vertical plane, and wherein one of said bearings is mounted on said bracket which provides the said downwardly facing surface.
 6. In a belt-type sanding machine, the improvement of claim 2, further characterized in that: said pad has a stepped configuration with an upper portion rising from a flange-like lower portion; wherein said horizontal wall with which the pad is connected has a hole of a size and shape to accommodate the upper portion of the pad but not its flange-like lower portion; wherein the upper portion of the pad projects through the hole in said wall and the lower portion of the pad underlies the underside of said wall; and wherein said means for adjusting the elevation of the pad and securing it in adjusted position comprises a plurality of screws passing downwardly through holes in said horizontal wall and threaded into holes in the flange-like bottom portion of the pad and by which the pad may be drawn upwardly with respect to said horizontal wall, and other screws having threaded connection with the flange-like lower portion of said horizontal wall and bearing against the underside of said wall to draw the pad downward.
 7. In a belt-type sanding machine, the structure set forth in claim 6, further characterized in that said spacer block has flat parallel top and bottom surfaces and in plan has substantially the same size and shape as the upper portion of the pad, so that when in operative position, the spacer block is substantially an upward continuation of the upper portion of the pad, and further characterized by handle means on the spacer block to facilitate its placement into and withdrawal from operative position.
 8. In a belt-type sanding machine, the improvement set forth in claim 2 wherein said clamping means comprises a clamping screw which passes freely through aligned holes in the substantially horizontal wall provided by the structure at the underside of the outboard end of the center bar and in the spacer block, and has a head bearing on said substantially horizontal wall and a threaded connection with said pad. 